android - 布局预览未呈现 - 可能是由于 androidx.widget

Question

Android Studio 中的布局预览未呈现，我不确定原因。我把所有东西都更新到最新版本了，在其他电脑上似乎也能正常运行。我的教授不确定如何解决这个问题，我能找到的所有其他布局渲染 Stack Overflow 帖子都已过时。我试过刷新它、重新启动它、重建它、使缓存无效等...

我能得到的最好线索是，它必须归因于 androidx.constraintlayout.widget.ConstraintLayout 没有得到正确支持。我的教授还提到 Jetpack 可能有问题？不太清楚他的意思。

activity_main.xml

    <?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity" android:background="@android:color/background_light">
    <EditText
            android:layout_width="86dp"
            android:layout_height="45dp"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/totalTwentyEditText"
            app:layout_constraintStart_toEndOf="@+id/totalFifteenEditText" app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintEnd_toEndOf="parent" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline4" android:text="0.00" android:textAlignment="center"
            android:focusable="false" android:longClickable="false"/>
    <androidx.constraintlayout.widget.Guideline android:layout_width="wrap_content" android:layout_height="wrap_content"
                                                android:id="@+id/guideline" app:layout_constraintGuide_begin="20dp"
                                                android:orientation="horizontal"/>
    <androidx.constraintlayout.widget.Guideline android:layout_width="wrap_content" android:layout_height="wrap_content"
                                                android:id="@+id/guideline2" app:layout_constraintGuide_begin="86dp"
                                                android:orientation="horizontal"/>
    <androidx.constraintlayout.widget.Guideline android:layout_width="wrap_content" android:layout_height="wrap_content"
                                                android:id="@+id/guideline3" app:layout_constraintGuide_begin="128dp"
                                                android:orientation="horizontal"/>
    <androidx.constraintlayout.widget.Guideline android:layout_width="wrap_content" android:layout_height="wrap_content"
                                                android:id="@+id/guideline4"
                                                android:orientation="horizontal"
                                                app:layout_constraintGuide_begin="191dp"/>
    <androidx.constraintlayout.widget.Guideline android:layout_width="wrap_content" android:layout_height="wrap_content"
                                                android:id="@+id/guideline5" app:layout_constraintGuide_begin="259dp"
                                                android:orientation="horizontal"/>
    <androidx.constraintlayout.widget.Guideline android:layout_width="wrap_content" android:layout_height="wrap_content"
                                                android:id="@+id/guideline6" app:layout_constraintGuide_begin="309dp"
                                                android:orientation="horizontal"/>
    <androidx.constraintlayout.widget.Barrier
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/leftColumn"
            app:barrierDirection="end"
            app:layout_constraintStart_toStartOf="parent"
            android:layout_marginStart="16dp"
            app:constraint_referenced_ids="textView3,textView5,textView4,textView2,textView"/>
    <TextView
            android:text="@string/bill_total"
            android:layout_width="wrap_content"
            android:layout_height="23dp"
            android:id="@+id/textView" android:textSize="18sp"
            android:textStyle="bold"
            android:textAlignment="viewEnd"
            android:textColor="@android:color/black"
            android:layout_marginStart="16dp"
            app:layout_constraintStart_toStartOf="parent"
            android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline"
            android:layout_marginBottom="8dp"
            app:layout_constraintBottom_toBottomOf="@+id/billTotalEditText"/>
    <TextView
            android:text="@string/tip"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/textView2" android:textSize="18sp"
            android:textStyle="bold" android:textAlignment="viewEnd" android:textColor="@android:color/black"
            android:layout_marginEnd="8dp" app:layout_constraintEnd_toEndOf="@+id/leftColumn"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline3"
            android:layout_marginBottom="8dp" app:layout_constraintBottom_toBottomOf="@+id/tipTenEditText"/>
    <TextView
            android:text="@string/total"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/textView3" android:textSize="18sp"
            android:textStyle="bold" android:textAlignment="viewEnd" android:textColor="@android:color/black"
            android:layout_marginEnd="8dp" app:layout_constraintEnd_toEndOf="@+id/leftColumn"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline4"
            android:layout_marginBottom="8dp" app:layout_constraintBottom_toBottomOf="@+id/totalTenEditText"/>
    <TextView
            android:text="@string/custom"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/textView4" android:textSize="18sp"
            android:textStyle="bold" android:textAlignment="viewEnd" android:textColor="@android:color/black"
            android:layout_marginEnd="8dp" app:layout_constraintEnd_toEndOf="@+id/leftColumn"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline5"
            android:layout_marginBottom="8dp" app:layout_constraintBottom_toBottomOf="@+id/customSeekBar"/>
    <TextView
            android:text="@string/tip"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/textView5" android:textSize="18sp"
            android:textStyle="bold" android:textAlignment="viewEnd" android:textColor="@android:color/black"
            android:layout_marginEnd="8dp" app:layout_constraintEnd_toEndOf="@+id/leftColumn"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline6"
            android:layout_marginBottom="8dp" app:layout_constraintBottom_toBottomOf="@+id/tipEditText"/>
    <EditText
            android:layout_width="302dp"
            android:layout_height="39dp"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/billTotalEditText"
            app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="8dp" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline"
            android:layout_marginStart="8dp" app:layout_constraintStart_toStartOf="@id/leftColumn"
            app:layout_constraintHorizontal_bias="0.0" android:text="@string/zeroDecimal"/>
    <EditText
            android:layout_width="81dp"
            android:layout_height="wrap_content"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/tipTenEditText"
            app:layout_constraintStart_toEndOf="@+id/textView2" app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintEnd_toStartOf="@+id/tipFifteenEditText" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline3" android:text="@string/zeroDecimal"
            android:textAlignment="center" android:focusable="false" android:longClickable="false"/>
    <EditText
            android:layout_width="86dp"
            android:layout_height="wrap_content"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/tipFifteenEditText"
            app:layout_constraintStart_toEndOf="@+id/tipTenEditText" app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintEnd_toStartOf="@+id/tipTwentyEditText" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline3" android:text="@string/zeroDecimal"
            android:textAlignment="center" android:focusable="false" android:longClickable="false"/>
    <EditText
            android:layout_width="86dp"
            android:layout_height="wrap_content"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/tipTwentyEditText"
            app:layout_constraintStart_toEndOf="@+id/tipFifteenEditText" app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintEnd_toEndOf="parent" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline3" android:text="@string/zeroDecimal"
            android:textAlignment="center" android:focusable="false" android:longClickable="false"/>
    <TextView
            android:text="@string/tenPercent"
            android:layout_width="36dp"
            android:layout_height="23dp"
            android:id="@+id/textView6" android:textSize="18sp"
            android:textAlignment="center" android:textStyle="bold" android:textColor="@android:color/black"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline2"
            app:layout_constraintStart_toStartOf="@+id/tipTenEditText" app:layout_constraintEnd_toEndOf="@+id/tipTenEditText"/>
    <TextView
            android:text="@string/fifteenPercent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/textView7" android:textSize="18sp"
            android:textAlignment="center" android:textStyle="bold" android:textColor="@android:color/black"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline2"
            app:layout_constraintStart_toStartOf="@+id/tipFifteenEditText" app:layout_constraintEnd_toEndOf="@+id/tipFifteenEditText"/>
    <TextView
            android:text="@string/twentyPercent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/textView8" android:textSize="18sp"
            android:textAlignment="center" android:textStyle="bold" android:textColor="@android:color/black"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline2"
            app:layout_constraintStart_toStartOf="@+id/tipTwentyEditText" app:layout_constraintEnd_toEndOf="@+id/tipTwentyEditText"/>
    <EditText
            android:layout_width="80dp"
            android:layout_height="45dp"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/totalTenEditText"
            app:layout_constraintStart_toEndOf="@+id/textView3" app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintEnd_toStartOf="@+id/totalFifteenEditText" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline4" android:text="@string/zeroDecimal"
            android:textAlignment="center" android:focusable="false" android:longClickable="false"/>
    <EditText
            android:layout_width="86dp"
            android:layout_height="45dp"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/totalFifteenEditText"
            app:layout_constraintStart_toEndOf="@+id/totalTenEditText" app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintEnd_toStartOf="@+id/totalTwentyEditText" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline4" android:text="@string/zeroDecimal"
            android:textAlignment="center" android:focusable="false" android:longClickable="false"/>
    <SeekBar
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:id="@+id/customSeekBar" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline5" app:layout_constraintEnd_toStartOf="@+id/customTextView"
            android:layout_marginEnd="8dp" app:layout_constraintStart_toEndOf="@+id/leftColumn"
            android:layout_marginStart="8dp" android:progress="18" android:max="100"/>
    <TextView
            android:text="@string/eighteenPercent"
            android:layout_width="55dp"
            android:layout_height="29dp"
            android:id="@+id/customTextView" android:textSize="18sp"
            android:textAlignment="center" android:textStyle="bold" android:textColor="@android:color/black"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline5"
            app:layout_constraintStart_toStartOf="@+id/totalTwentyEditText" app:layout_constraintEnd_toEndOf="@+id/totalTwentyEditText"
            android:layout_marginBottom="8dp" app:layout_constraintBottom_toBottomOf="@+id/customSeekBar"/>
    <EditText
            android:layout_width="84dp"
            android:layout_height="43dp"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/tipEditText" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline6"
            app:layout_constraintEnd_toEndOf="@+id/totalTenEditText"
            app:layout_constraintStart_toStartOf="@+id/totalTenEditText"
            android:text="@string/zeroDecimal" android:textAlignment="center" android:focusable="false"
            android:longClickable="false"/>
    <TextView
            android:text="@string/total"
            android:layout_width="51dp"
            android:layout_height="26dp"
            android:id="@+id/textView10" android:textSize="18sp"
            android:textStyle="bold" android:textAlignment="viewEnd" android:textColor="@android:color/black"
            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="@+id/guideline6"
            android:layout_marginBottom="8dp" app:layout_constraintBottom_toBottomOf="@+id/tipEditText"
            app:layout_constraintStart_toStartOf="@+id/totalFifteenEditText" app:layout_constraintEnd_toEndOf="@+id/totalFifteenEditText"/>
    <EditText
            android:layout_width="86dp"
            android:layout_height="47dp"
            android:inputType="numberDecimal"
            android:ems="10"
            android:id="@+id/totalEditText" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="@+id/guideline6"
            app:layout_constraintStart_toStartOf="@+id/totalTwentyEditText"
            app:layout_constraintEnd_toEndOf="@+id/totalTwentyEditText"
            app:layout_constraintBottom_toBottomOf="@+id/textView10" android:text="@string/zeroDecimal"
            android:textAlignment="center" android:focusable="false" android:longClickable="false"/>
</androidx.constraintlayout.widget.ConstraintLayout>

应用程序等级

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.example.tipcalculator"
        minSdkVersion 17
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

如有任何帮助，我们将不胜感激。

Answer 1

我可以看到你的实现是错误的:

com.android.support.constraint:constraint-layout:1.1.3

你应该:

androidx.constraintlayout:constraintlayout:2.0.0-alpha3

还有一些其他的，比如:

com.android.support:appcompat-v7:27.1.1

修复所有转到 Refactor(menu)->migrateToAndroidX如果您没有这样的选项，请更新您的 ide(Android Studio)。